Need help!! Sick chicken, breastbone protruding, she's not eating, advice pleass (2024)

I have 3 hens (Easter egger and Bantam - 2 1/2 yrs old and a Sapphire Gem - 1 1/2 yrs old). I got my EE and Bantam at the same time at TS, then a year later I got a Sapphire Gem from TS as well and when she got old enough I slowly integrated her in with the other 2 and for the most part they all get along...so here's the problems. My Sapphire Gem used to lay pretty light brown eggs but stopped last summer and hasn't laid an egg on her own (I gave her some calcium last fall for a few days and she did lay a couple eggs with that) and then winter was here so I quit giving it to her so she could rest. Other then that she's always seemed healthy, alert, normal acting. Although at times my EE has and does bully her some in which I stop that every time I see it and have even separated the EE overnight (time out/jail) and it does help.
My other 2 hens have been back to laying for months and she still hasn't but seems healthy otherwise. A month ago I saw my Bantam in a lot of distress and quite frankly was in the middle of dieing when I gave her a dose of Valbazen and in like 2-3 minutes she was up walking around acting normal!! I just couldn't believe it, so I gave a dose to the other 2 at that time since I was pretty certain they probably had them as well. I gave all 3 of them another dose a few days later. After all of that I had to move, so my 3 chickens had to be moved out to my sister's, which also has chickens. We closed off a section for them by using hardwire cloth between them. Which has worked out but now my EE (top layer) has stopped laying?? and a couple days ago I picked up my SG and I could feel her breastbone protruding alot and she was very light, too light.
She's been active but thinking back the last couple days she has been acting a little slower, and this morning I go up there and she's up and walking around but still slowly while pecking the ground. She did not eat but saw her get a few little drinks of water and then she walked off and she's standing over by the dust bath, just standing there.
I can tell by the way she is acting it's not good and I need to do something immediately. Her comb is a bright red color standing upright, he does have a nasty butt, I didn't see much poop under the perch last night where she usually sleeps, I've got some pictures of their poop, I can't tell if it's worms or not!?? I'm sick to my stomach and very concerned and worried and been researching non stop trying to figure out what could be wrong and how to treat her!! So if anybody has any suggestions, please let me know!! It will be greatly and much appreciated as I'm running out of time. I've looked up and read so much but I'm still puzzled, confused and not sure what to think or do and just stressed out!!

Is this it?

Yes. That's the stuff! Pick up a bottle of Poultry Nutri-drench while you're there. But don't give these vitamins during the Corid treatment. Give her a dropper full each day between the Corid rounds. I like to sprinkle them on boiled rice. That should help put some weight back on her. Break a raw egg over the rice, as well. When you feed it to her, it helps to have one of her friends dine with her as it stimulates the weaker chicken to eat having a little dining partner. Start the boiled rice and egg right away. Save the vitamins for later.